2.2 Definitions – Physical Properties

Physical Density Color Luster Transparent property /Opaque Smell Viscosity High Low Malleability Viscosity Viscosity Brittle Conductivity High Insulators Conductors Conductivity Low Solubility High Low Conductivity Solubility Solubility Melting Boiling point Vaporization Condensation Filtration

Physical Property - characteristic of a substance that can be observed without changing the substance.

Examples: Viscosity, Conductivity, Malleability, Melting Point, Boiling Point, Density, , smell, opacity, transparency, color,how light interacts with a substance, Specific heat ( how easily a substance changes temperature)

Physical properties are used to identify substances.

What is this substance?

Since we can only see it in the photo we are limited by its appearance. If we could hold it we might get a better idea by its (density)

Just from looking we can see its: COLOR LUSTER – the way in which light interacts with the surface (Shiny?, Earthy? Metallic?) Transparent? Does light pass through it? Can you see through it?

The opposite of Transparent is Opaque – Light does not path through it.

SMELL – If you were to smell this substance you would find it has none.

This substance is Fool’s Gold, also known as Iron pyrite. Density could tell us the difference.

Density of Gold (in nature) = 19.3 g/cm3 Density of Iron Pyrite = 4.8 g/cm3 In this case we can measure the density and determine the material.

Density and Floating

Investigate how density of a liquid or object changes how things float. Can a cannonball float?

Cannonball floating on Liquid Mercury: http://www.youtube.com/watch?v=Rm5D47nG9k4&list=PL072C9B991AE3D15E&index=1

Floating Lead: http://www.youtube.com/watch?v=t1Hv0Oz_r1k&list=PL072C9B991AE3D15E

Floating on the Dead Sea: http://www.youtube.com/watch?v=aTcyACmiaho

Density – the quantity of mass per unit volume. The density can be expressed mathematically as : 푚 휌 = 푉 where ; ρ = Density (grams/cm3),V= volume ( cm3), m = mass (grams)

This equation can be algebraically solved for mass and volume to create two alternate forms of this equation. Take a moment to solve this equation for m and V.

UNITS (just plug the units into the equation)

푚 푘푔 푚 푔 휌 = = or 휌 = = 푉 푚3 푉 푐푚3

Viscosity – a measure of how easily a liquid flows or how much the fluid resists movement through itself.

High Viscosity Low Viscosity Flows slowly Flows quickly Examples – Examples- Room temperature honey Water Pine pitch gasoline

Effect of Temperature - in general substances are more viscous when the are colder.

We say that “Viscosity is a function of temperature.” If we were to plot viscosity and temperature, which one is the :

Independent Variable: Dependent Variable:

Therefore the graph will be Viscosity vs Temperature. Which value is on the x axis?______

This graph illustrates how motor oils viscosity changes as its temperature changes. http://www.getrolling.com

Let’s take a look at what this all means: Dropping objects in different fluids: http://www.youtube.com/watch?v=3KU_skfdZVQ Viscosity Race https://www.youtube.com/watch?v=977wNbFiYlc Conductivity – a measure of how well a substance allows the flow of energy (heat or electricity)

High Conductivity Low Conductivity Energy flows well Energy does not flow well Copper heats up quickly Glass does not heat up quickly. Copper allows electricity to flow Glass stops the flow of electricity. well. Copper and other metals are Glass is an insulator. conductors.

Heat Conductors vs Insulators: http://www.youtube.com/watch?v=pyfM_fKSICE

Conductivity of metals: http://www.youtube.com/watch?v=RHQ17S72ON4

Malleability- a measure of how well a substance can be bent without breaking

Malleable Brittle Substances that can be bent or Substances that break quickly when stretched a long distance before bent or stretched breaking Steel, copper, gold Glass, Hardened steel, quartz , These substances are desirable for These substances are often used due making things like jewelry because to their strength and resistance to they can be worked in to various changing shape. shapes.

How Aluminum Foil is made: http://www.youtube.com/watch?v=4W4Ca7x7Z7s Making Aluminum Cans: http://www.youtube.com/watch?v=V7Y0zAzoggY

Look what malleable metals can do: https://www.youtube.com/watch?v=8qGHWZm0C-o

Making a huge dish from Metal https://www.youtube.com/watch?v=UFzxgSD4DRE

How is Chain made? (COOLEST MACHINES EVER!!!) https://www.youtube.com/watch?v=a9O_kGbEsW8

Melting/Freezing Point – the temperature at which a substance being heated changes from a solid to a liquid.

This is the same as the freezing point, the temperature at which a substance being cooled changes from a liquid to a solid.

melting

SOLID LIQUID

freezing Melting Points of Some Common Liquids Liquid Melting Point (F) Melting Point ( C ) Water 32 0 Alcohol -173 -114

When liquids have a different melting point, they can be separated by freezing one but not the other. This is called Fractional Freezing.

Making Apple Jack: A New England Tradition (start at 2:20 for freeze distillation) http://www.youtube.com/watch?v=CGd5_rx9dE8

There is a history connection here. What products could people make from Apples?

Boiling/Vaporization or Condensation Point – the temperature at which a substance being heated changes from a liquid to a gas. Or if being cooled the temperature at which it condenses.

Vaporization

LIQUID VAPOR

Condensation

Boiling Points of Some Common Liquids

Liquid Boiling Point (F) Boiling Point ( C ) Water 212 100 Alcohol 173 78

When mixed liquids have a different boiling point, they can be separated by boiling one but not the other. This is called .

Fractional Distillation is used to separate crude oil into its useful components: Tar for roads Gasoline for cars Heating oil for homes Diesel for cars and larger engines like trains Jet fuel

Distillation of Oil: http://www.youtube.com/watch?v=KCs1F_44dy4

Solubility – the ability of a substance to dissolve in a liquid. The liquid may or may not be water.

Graph from: http://www.sciencegeek.net/Chemistry/taters/solubility.htm

High Solubility Low Solubility A lot will dissolve Not much will dissolve

Physical Change – some properties change but the substance is still the same.

When liquid water freezes its properties change but it is still water. It is still made up of 2 hydrogen atoms and one oxygen.